1 #include <iostream>

 2 #include <cstdio>

 3 #include <cstring>

 4 #include <cmath>

 5 #include <algorithm>

 6 #include <stack>

 7 #include <queue>

 8 #include <vector>

 9 #include <map>

10 #include <set>

11 #include <unordered_set>

12 #include <unordered_map>

13 #define ll long long

14 #define fi first

15 #define se second

16 #define pb push_back

17 #define me memset

18 const int N = 1e6 + 10;

19 const int mod = 1e9 + 7;

20 using namespace std;

21 typedef pair<int,int> PII;

22 typedef pair<long,long> PLL;

23

24 int n;

25 ll cnt=0;

26 ll r,g,b;

27 string s;

28

29 int main() {

30     ios::sync_with_stdio(false);

31     cin>>n>>s;

32    for(int i=0;i<n;++i){

33        for(int j=i+1;j<n;++j){

34            int k=j+(j-i);

35            if(k>n-1) continue;

36            if(s[i]!=s[j] && s[j]!=s[k] && s[i]!=s[k]) cnt++;

37        }

38    }

39

40    for(int i=0;i<n;++i){

41        if(s[i]=='R') r++;

42        else if(s[i]=='G') g++;

43        else b++;

44    }

45    printf("%lld\n",r*g*b-cnt);

46

47

48     return 0;

49 }